The invention relates to a method of providing a patterned relief of cured photoresist on a flat substrate surface, said substrate surface being provided with a layer of a UV-light curable liquid photoresist, after which said photoresist is brought into contact with a UV light-transparent mould having a relief which is complementary to the patterned relief to be provided and is subsequently cured by exposure to a UV-light source, thereby forming said patterned relief, after which the mould is removed from the cured relief.
The invention also relates to a device for carrying out such a method.
Such methods are used, for example, in the manufacture of flat screens for liquid crystal display devices (LCD and LC-TV) in which the patterned relief consists of the so-called black matrix between the colour filters. The method can also be used in the manufacture of patterned reliefs on screens of flat colour display tubes, such as flat cathode ray tubes and electron-fibre displays. Said method can further be used to provide a flat TV screen with a defined roughness in order to reduce reflections (anti glare).
Such a method is known from Patent Abstracts of Japan JP-A-3-54569. In the known method, a drop of liquid photoresist is provided between a flat substrate and a flat mould, said mould having a patterned relief in the form of recessed areas which are complementary to the relief to be provided in the form of protruding parts. The mould and the substrate are pressed together causing the photoresist to spread out over the entire substrate surface. The photoresist is cured by exposure to UV light, exposure taking place through the substrate or through the mould. After the photoresist has been cured, the mould is removed from the substrate, leaving the complementary pattern of the relief of the mould in cured photoresist on the substrate. In literature, this known method is referred to as replication. The protruding parts of the relief formed have dimensions of, for example, 10.times.10 .mu.m. Cured photoresist is also present between the protruding parts of the cured relief, said photoresist must be removed by a uniform etching treatment.
The known method has a number of drawbacks. The known method is unsuitable for providing a relief pattern on large surfaces of, for example, 1.times.1 m; it is limited to dimensions of maximally 30.times.30 cm. At larger dimensions, detaching the mould from the cured photoresist becomes problematic owing to the action of large adhesive forces. Despite the use of a release agent, the release of large surfaces requires substantial forces, so that the substrate and/or mould may become damaged. A flexible substrate and/or mould can be more readily released, however, frequently flexible substrates and/or moulds are impossible or undesired, for example, to attain a reproducible precision. To provide larger surfaces with a relief, in principle, said relief can be built up of a number of juxtaposed replicated surfaces. However, said method has the disadvantage that the replicated surfaces must be accurately juxtaposed to avoid the formation of visible seams caused by misfitting contiguous reliefs. A further drawback of the known method is the risk that air bubbles are included in the liquid photoresist when the mould and the substrate are arranged on top of each other. This risk increases with the dimensions of the surfaces to be replicated. A further drawback of the known method is the above-mentioned necessary etching treatment to which the cured photoresist must be subjected in order to remove the photoresist between the protruding parts of the relief.